1. Field of the Invention
This invention relates to a semiconductor device comprising a high-resistance substrate with for example, a high-frequency circuit formed thereon.
2. Description of the Related Art
Recently, a system-on-a-chip comprising a semiconductor chip on which a plurality of LSIs are formed has been developed. With the development of the system-on-a-chip, not only a digital circuit and a low-frequency analog circuit, but also a high-frequency circuit are formed on a single substrate. When a high-frequency circuit is formed on a silicon substrate, it is preferable to use a substrate having a high resistance. For example, if an inductor is included in the high-frequency circuit, the Q value of the inductor can be increased. In addition, it is possible to prevent interference between the inductor and the other circuits. Also, even if a resistor or capacitor is coupled to the substrate, it is possible to prevent a signal from leaking into the substrate.
When the concentration of dissolved oxygen in the substrate is high, the oxygen is converted into a donor form and the resistance of the substrate is reduced if heat treatment is used when formatting a device. Therefore, a high-resistance substrate is formed and the concentration of dissolved oxygen in the substrate is reduced. However, if the concentration of dissolved oxygen is reduced, slips occur in the peripheral portion of the rear surface of the substrate during heat treatment. The slip starts in a portion in contact with a portion supporting the wafer used as the substrate when the wafer is heat treated in a vertical furnace. If the slip reaches a device formation region of the front surface of the wafer, a leak occurs and it becomes difficult to form a satisfactory device.
An example is given in which an SOI device is formed on a high-resistance substrate (for example, refer to 2000 SYMPOSIUM ON VLSI TECHNOLOGY Digest of Technical Papers pp. 154-155, Jun. 13-15, 2000), although this example is different from an example in which devices are formed in bulk.
Thus, to improve the performance of the high-frequency circuit, it is extremely important to increase the resistance of the substrate. However, if the concentration of dissolved oxygen in the substrate is reduced to form a high-resistance substrate, there is a risk of slips starting in portions supporting the substrate during such heat treatment as an annealing process. Therefore, there is a pressing need to develop a semiconductor device in which the occurrence of slips can be suppressed and a device can be formed on the high-resistance substrate